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def countMaximumDays(lend, payback):
    from bisect import bisect_left

    n = len(lend)
    # Create a list of lenders with their lend amount and payback
    lenders = sorted(zip(lend, payback))
    lend_amounts = [l[0] for l in lenders]

    day = 0
    prev_payback = 0  # No payback on the first day
    start_idx = 0

    while True:
        if day == 0:
            # On the first day, pick the lender with the smallest lend amount
            lend_i, payback_i = lenders[start_idx]
            start_idx += 1
            prev_payback = payback_i
            day += 1
        else:
            # Need to find a lender with lend >= prev_payback
            left = bisect_left(lend_amounts, prev_payback, lo=start_idx)
            if left == n:
                break  # No lender can satisfy the payback requirement
            lend_i, payback_i = lenders[left]
            start_idx = left + 1
            prev_payback = payback_i
            day += 1
    return day